This invention relates to the temporary storage of hotmix asphalt. More particularly, this invention relates to hotmix storage facilities equipped with a system for injecting inert gas interiorly of the bin to prevent oxidation of hotmix asphalt.
The advantages associated with the temporary storage of hotmix asphalt have long been recognized in the industry. Such storage permits a readily available supply of asphalt for discharge to delivery trucks which carry the material to a job site. Thus truck waiting time at the asphalt plant, along with the attendant costs thereof, is greatly minimized.
Experience shows that oxidation of the asphalt occurs during storage which represents product degradation and also presents unloading difficulties. To minimize such harmful oxidation, it is known to provide an inert gas interiorly of the bin as a "blanket" over the asphalt to prevent contact with air.
U.S. Pat. No. 3,834,595 issued Sept. 10, 1974 to Brock et al. and U.S. Pat. No. 3,820,687 issued June 28, 1974 to Brock are representative of developments in the state of the art of providing an inert gas atmosphere in an asphalt storage bin. Both references teach the use of inflatable bladders to seal the openings of the storage bin to provide a completely sealed chamber in which an inert gas is contained. The Brock U.S. Pat. No. 3,820,687 prevents asphalt oxidation by circulating air within the bin through a converter in which burning carbon converts the oxygen present in the air to inert carbon dioxide.
The inert gas systems of the prior art are characterized as an inert gas continuously supplied to a tightly sealed storage bin. Costly and complex equipment is required to carry out this intent. Our invention, on the other hand, departs dramatically from such concepts. There is a need for a simple, inexpensive and reliable system to retard oxidation of hotmix asphalt in a storage bin. The primary goal of this invention is to meet this need.
More particularly, an object of this invention is to provide a top closure door for an asphalt storage bin which is self-sealing in a closed position, but which is quickly opened to admit asphalt fed from the production plant.
Another object of the invention is to provide convenient discharge of hotmix from a storage bin equipped with an inert gas system and to eliminate the creation of a partial vacuum in the top of the storage bin when material is discharged.
An additional object of the invention is to provide an inert gas injection system to effectively retard oxidation of asphalt within the storage bin while minimizing the demand on the inert gas supply itself. In other words, economy of operation is of paramount importance. Minimal inert gas demands are achieved through a unique systems control which electrically times the injection of inert gas.
Another object of the invention is to provide an inert gas system of the character described and which functions trouble-free with little maintenance and repair.
Other and further objects of the invention, together with the features of novelty appurtenant thereto, will appear in the course of the following description.